Electronic assemblies are built with a multitude of light-emitting components, primarily light emitting diodes (LED's), to indicate functions, or faults occurring on the assemblies. In addition to light, information on the nature of the operations of faults on these assemblies is conveyed by the color emitted by the devices. Light emitting diodes are available in colors covering the entire visible spectrum as well as white.
Various methods have been implemented to verify the correct operation of these light-emitting components, from test sequences where human verification is used, to photo detectors employed to perform the tests automatically.
Human verification is slow and unreliable. While photodetectors can easily verify that light is present, validation of the correct color has become extremely important. Photodetectors employing narrow bandpass color filters have been employed to test for the proper emitted wavelength, with limited success, since variations in output levels of the photodetector cannot discriminate intensity from colors approaching the edge of the passband. This becomes critical in the very narrow color bands in the visible spectrum.
In addition, these implementations require that each photodetector be customized for the particular wavelength of the light-emitting component under test, adding lead time and expense to their use. Current photodetector solutions are available in various configurations, some having the detector itself mounted near the light-emitting component, where others use fiber optic cable to collect the light and present it to a remotely mounted photodetector. Consequently, a need exists for a test module for automated test equipment to test light emitting components which addresses the problems associated with prior test apparatus.